As more and more electronic devices are being used, electromagnetic interference is getting more and more serious, greatly affecting the application of other devices. Therefore, it has become really necessary to measure the electric field distribution around a device and take anti-interference measures. Conventional electric field measuring system adopts an electrical active metal sensor. However, the metal parts of the electrical sensor, such as the metal probe and coaxial cable, can cause serious distortion to the electric field to be measured, resulting in high measurement result error. Besides, the actual electric field interference generally covers wide band from several kHz to tens of GHz. In addition, the conventional electrical sensor can operate only at a certain frequency point within a narrow range, which limits its measuring bandwidth. In order to overcome the limitation of the conventional electrical sensor, researchers have utilized crystal with linear electro-optical effect, such as lithium niobate to make an integrated optical electric field sensor, which has the advantages of high sensibility, wide bandwidth, and small footprint.
Currently, research on integrated optical electric field sensor primarily focuses on one dimensional measurement, which is only applicable to clear measurement of the electric field direction. However, the actual direction of the electric field to be measured is generally unknown. If the polarization direction of the antenna of the sensor is inconsistent with the direction of the electric field to be measured, the electric field amplitude obtained from the measurement is the projection of the actual electric field in the polarization direction of the antenna, which cannot accurately reflect the amplitude information of the actual electric field. Even if the direction of the electric field to be measured has been known, the electric field to be measured can be a variable field, of which the direction may change anytime, and it's impracticable to manually change the layout direction of the sensor either.
Therefore, only when an electric field sensor can measure electric field with more than one dimension, it can satisfy the requirement of actual electric field measurement. Parallel plane electric field and spherical surface electric field are the examples of two dimensional electric field. For example, Chinese patent application No.201210348311.8 discloses an integrated electric field sensor based on common path interference, comprising a lithium niobate substrate, a silicon substrate, a shim, a detecting unit and a modulating unit, wherein the lithium niobate substrate and silicon substrate are connected with each other through an ultraviolet curing adhesive, and are respectively connected with the shim through the ultraviolet curing adhesive. The detecting unit comprises two upper contact electrodes, a connecting conductor and two dipole antennas; the modulating unit comprises two lower contact electrodes, an optical waveguide and two modulating electrodes. In that patent, the construction of the integrated electric field sensor is complex with high measurement error and low measurement accuracy.